The present invention relates generally to testing bonding strength between a floor and tiles cemented to the floor, and more specifically is an improvement over the apparatus and method set forth in U.S. Pat. No. 4,823,611 to Young.
It is desirable to test the adhesion strength of cement used to bond tile to an underlying floor. One approach to this problem has been set forth in the aforementioned patent to Young. However, such device in actual usage has shortcomings which can produce inaccurate test results. For example, the Young device tends to pop out of the space between the two tiles being used in the test (reaction tile and test tile) when pressure is applied by the Young device on the tiles. As a result, operators of the Young device sometimes will actually stand on top of the device during operation to prevent it from popping out of the tiles. Such technique significantly distorts the accuracy of the data generated from the Young device.
The present applicant has concluded that two contributing causes to such inaccurate data from the Young device include: (1) force exerted in bending the Young device; and (2) frictional force between the Young device and the floor due especially to the operator standing on the Young device. Each of these problems tend to make the pressure readout on Young artificially higher since the readout actually reflects three forces: the force to bend the Young apparatus frame, frictional forces, and the force to overcome the tile-floor bond. However, with the first two forces not being accounted for, the Young readout tends to inaccurately suggest the tile-floor bond strength is greater than it actually is.
The present invention seeks to overcome these disadvantages of the Young apparatus and method, resulting in more accurate test data. Selected features of the present invention which help overcome these problems include the use of a swivel jaw to engage the face of at least one tile. Accordingly, if the faces of the two tiles to be engaged are not perfectly in alignment, the swivel jaw will compensate, thereby eliminating any eccentric or off-center forces which would tend to bend, twist, and distort the frame. Thus, undue forces are not introduced to bend the frame. Second, a more rigid frame is provided taking into account the cross-sectional moments of inertia along bending axes to provide greater rigidity. With this more rigid frame, less twisting or bending is likely to occur, resulting in more accurate test results. Third, the present invention is arranged so the test apparatus is bridged between the two tiles, rather than resting on the floor, avoiding any frictional forces between the test apparatus and the floor. Fourth, the present invention utilizes a more precise pressure readout with finer increments, allowing for greater precision of data. And fifth, the ram which moves the reaction head and the movable head apart is located on the bottom third of the heads, near the same plane as the tile being tested, to reduce eccentricity and associated bending of the test apparatus frame.